I use Pandora.com.
You can create as many stations( genre) as you like. You can also mix those channels together.
Type in a group you like, it will play selected songs from that group as well as those like it.
If a song comes up you don't like, you can choose to delete it so it never comes up again.There is also the option of buying from I tunes or Amazon. You can , when hearing a group you like, pull up there albums and listen to short downloads.